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2So                        EOCENE AND MIOCENE PIGS                       CHAP.
of dependent processes near the symphysis, which suggest pro-
cesses occupying a corresponding position in Dinoceras. The
skill and body are heavy, but the two-toed limbs are slender.
There Is a smaller pair of toes behind these. The dentition
is complete, and the canines are not inordinately developed.
The brain is very diminutive. Perhaps JS. uintense should be
.separated as a distinct genus, Protelotherium}
Ifyotherium (which is regarded as identical with Palaeochoerus")
has a sharp sagittal crest; the orbit is nearly but not quite
closed. The canines are not strongly developed. The upper canines
have double fangs as in Triconodon among extinct mammals,
and as in the Hedgehog and other forms among living Mammalia.
The premolars have the cutting and serrated edge of those of some
other Pigs, a feature which gives them a curious resemblance to
the " grinding " teeth of Seals. The molars are tuberculate, and
like those of living Pigs, It is European, and Indian in range,
and Miocene.
The genus Choeroyotamus has a complete dental formula save
for the loss of a premoiar in the lower jaw. Though it has lost
this tooth, it is from an older stratum than some of those
forms which have retained that premoiar ; it has been found
in the Upper Eocene of the Isle of Wight and of the neighbour-
hood of Paris.
The American and Miocene Chaenohyus has lost the corre-
sponding teeth of the upper jaw.
Jlomacodon2 is a genus consisting of several species, which
has a btmodont and complete dentition. The molars are sex-
tubercular in the upper jaw. S. vagans "was of about the size
of a [Rabbit, and it appears to have had a curved neck. The
limbs had five digits, as is so generally the case with Eocene
Ungulates- It is known from the Middle Eocene of Wyoming.
The Selenodontia or Huminantia form the second division of
existing Artiodactylea The characters of the teeth, which give
them- their name, have already been referred to. They also
differ In that there are never more than a single pair of incisors
* Osbonv &OL Amer, Mw&. Nat. JEKst. vii. 189S, p.^102.
. Jfaurn. Sci. xfriii╗ 1894y jpu 262.*